I thought so, but I do worry about inquizitive Hedgepigs getting a clout on the snout, and of course the bat problem.
I have no idea how to help though.
Mail me all spare pallets, bearings and cap-screws? or obtain knowledge of electronics for charging systems quickly? lol
I look forward to seeing a picture when you figure it out.
If I can afford it I intend to write it up as an open source project if It gets off the ground, We'll see what the scrappy has to offer by way of bicycle hubs on Tuesday, I refuse to pay upwards of £10 each and I'll need 2 I sure aint buying new ones.
Thanks for that link, I'd not actually looked into the bat problem that hard yet, it's just something I learned on QI and thought I'd best do the math.
As for the "Sail effect" If my calculations are correct, even with a 20M s-1 wind I'd suggest only a 25Kg force, (Though I've been working from a real old textbook from my college days, and with these things I find that experience if survived is always the best learning tool
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on the sails assuming an air density of 1Kg M-3 Though I'm going to have to re-look at that math, what I've givven here is just from memory and may well be the results from the KE equasion, and if that's the case I'll be needing to find a better motor for use as the genny/alternator, in the first instance I think I have an old moped one, but dependent upon it's output I may need to waste some energy stepping it up (6V electricals on the ped
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A bit of rooting around found wikipedia article on drag coefficient, which gives formula Force = 1/2 * (density of air) * (speed)^2 * (drag coefficient).
Air density 1.25 kg/m^2 from a neat source, Physics Factbook http://hypertextbook.com/facts/2000/RachelChu.shtml and drag coefficient approx 1 - max of about 2 per the wikipedia article for a flat plate perpendicular to the wind direction (blades stopped).
Blade area 16in x 6in times four blades = 0.25 sq meter means force of 340 N. Suppose center of moment arm located 2 meters above ground? Or maybe less, as you have a low profile design?
Anyway, my rough calc using extreme values checks with yours.
One other thought - about the whack-hedgehog-on-head concern. It is not as visually appealing, but a vertical rotor might be safer and less footprint. Seen sometimes in curbside advertising signs.
Odd you should mention vertical rotors, There's a whole lot of metalwork involved in those street-signs that I no longer have the access to equipment for, I did however make an "annemometer-style" "Toy mill" just recently by bolting (Couldn't find my rivet pliers) 3 of her yoghurt pots to a 50CD spindle. it's ok in gusts of wind, I'm a tad concerned as to whether I'll add too much weight (Considering the "bearings" are the inner of the plastic spindle and a 6" nail) for it to spin in lighter breezes if I added another 3 pots.
Now I've found my pop-rivit pliers I may well try for the hell of it, but I do reccon that unshielded verticles will be less efficient than verticle fitment, at least in a vertical fitment all the wind in the right direction is working for you, not against 1/3 the input (guestimate figures) and I'll bet a 12" gap between deck and blade edge will offer more than enough hedgehog space, we'll see.
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I thought so, but I do worry about inquizitive Hedgepigs getting a clout on the snout, and of course the bat problem.
I have no idea how to help though.
Mail me all spare pallets, bearings and cap-screws? or obtain knowledge of electronics for charging systems quickly? lol
I look forward to seeing a picture when you figure it out.
If I can afford it I intend to write it up as an open source project if It gets off the ground, We'll see what the scrappy has to offer by way of bicycle hubs on Tuesday, I refuse to pay upwards of £10 each and I'll need 2 I sure aint buying new ones.
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http://www.scientificamerican.com/article.cfm?id=wind-turbines-kill-bats&print=true
It looks to me, from reading the article, that there is no concern with moderate-sized windmills like the one you are planning.
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Wow, a research buddy :)
Thanks for that link, I'd not actually looked into the bat problem that hard yet, it's just something I learned on QI and thought I'd best do the math.
As for the "Sail effect" If my calculations are correct, even with a 20M s-1 wind I'd suggest only a 25Kg force, (Though I've been working from a real old textbook from my college days, and with these things I find that experience if survived is always the best learning tool ( ... )
Reply
on the sails assuming an air density of 1Kg M-3 Though I'm going to have to re-look at that math, what I've givven here is just from memory and may well be the results from the KE equasion, and if that's the case I'll be needing to find a better motor for use as the genny/alternator, in the first instance I think I have an old moped one, but dependent upon it's output I may need to waste some energy stepping it up (6V electricals on the ped ( ... )
Reply
Air density 1.25 kg/m^2 from a neat source, Physics Factbook http://hypertextbook.com/facts/2000/RachelChu.shtml and drag coefficient approx 1 - max of about 2 per the wikipedia article for a flat plate perpendicular to the wind direction (blades stopped).
Gusting peak (??) lower limit from http://www.knmi.nl/samenw/hydra/faq/press.html and other pages there - say 33 m/s.
So that calcs to 1360 newtons/sq meter peak case.
Blade area 16in x 6in times four blades = 0.25 sq meter means force of 340 N. Suppose center of moment arm located 2 meters above ground? Or maybe less, as you have a low profile design?
Anyway, my rough calc using extreme values checks with yours.
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Now I've found my pop-rivit pliers I may well try for the hell of it, but I do reccon that unshielded verticles will be less efficient than verticle fitment, at least in a vertical fitment all the wind in the right direction is working for you, not against 1/3 the input (guestimate figures) and I'll bet a 12" gap between deck and blade edge will offer more than enough hedgehog space, we'll see.
Reply
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